So I bought a flathead out of a generator year back, was running well. I am now building the '26 roadster it is going into. I have the motor on a stand to "clean it up" and get ready to buy any needed parts. As it was in a generator there was no pressure plate, just a clutch disk and flat plate mounted to hold in place. So here I am getting ready to order clutch/pressure plate. I researched the bolt hole pattern for both 9" and 10" clutches... AND my 1939/40 59A has what appears to be a 1949+ flywheel. I measured the bolt pattern and sure appears to be '49+. See photos. (yes I am taking it off to get resurfaced) I have a rebuilt 3 speed top loader (open driveline) ready to bolt up. Question is can I use my 3 speed transmission and buy a 49+ clutch /pressure plate? such as one like this - https://www.speedwaymotors.com/Flat...sc-with-Long-Style-Pressure-Plate,414455.html
I've never tried it, but supposedly it does't work. Ring gear in the wrong place or sumthin. 8ba flywheels have the PP bolt holes drilled all the way thru, and early motors have blind holes.
Blind holes definitely suggests earlier. Also, I believe the ring gear on an 8ba is 5/8" wide, whereas earlier ring gear is 7/8" wide. So that is something else to help confirm what you have. Here are links to three Hamb threads I found helpful when I was trying to matchup my flathead/flywheel/clutch: https://www.jalopyjournal.com/forum/threads/tech-help-flathead-clutch-question.277086/ https://www.jalopyjournal.com/forum/threads/8ba-and-39-trans-clutch-question.488085/ https://www.jalopyjournal.com/forum/threads/39-tranny-to-late-mercury-flathead.478323/
This is what I am told an early flathead 10" PP measures at (see photos sent to me for reference) Why if my PP bolt holes measures almost an inch more can it be considered an early flywheel? Confused
well I may have my answer "If you have a 1940 Ford flywheel with an 11-1/2” pressure plate bolt circle, it is most likely from a truck or a heavy-duty application. The standard 1940 Ford passenger car flywheel used a 9” clutch and a smaller bolt circle. Larger bolt circles, such as 11-1/2”, were typically used for bigger clutches found in trucks or commercial vehicles from that era. This configuration allowed for the use of 10” or 11” Long-style pressure plates, which were designed for higher load capacities."
So, you have a truck flywheel. You could use it, but the whole assembly is heavier, and hard on the left leg. Have it drilled for a 10", or some say 9"
Better yet, find a car application flywheel from a 35-40 that has the 9" pp pattern already there... it will have a lip around the edge, with it machined off, it will be even lighter than a "truck" flywheel. Those two combined would be the lightest flywheel/pp combo next to going to aftermarket.
You can buy a 49-53 style aluminum flywheel from fidanza, which will be drilled for multiple PP . I have a 27 T roadster with a 40 flathead and one of these 12 pound flywheels. I had to put a 1/4" spacer in the starter bendix to keep it from chattering on the ring gear. No big deal, winds up fast and works great. The friction surface is steel and it comes to you painted, remove the paint or it will turn into glue on the first run.
I've posted this before, but I have the flywheel @big duece shows, with the blob cut off and 9" in my avatar 34. This was done from info from the late great Rumble seat, and Bruce Lancaster writings. My clutch assembly was all new from Ft. Wayne when they were still made in house, no chinesium junk. It will slip at low RPM's, mid range once the centrifugal weights kick in, no slip. Motor is just a 59a, merc crank and cam, single carb, not a fire breathing monster. I believe its a weak PP from FT Wayne, but have not yet had it apart to measure spring pressure. Its on the list...but the list is long. Ya know, it works...don't fix it
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